Did you know there’s a medical term for women who rely on the rhthym method? They’re called ‘mothers’.
I sold my soul to Satan for a dollar. I got it in the mail.
Odds of getting pregnant are increased porportionately by the amount of alchohol consumed.
Regardless of all the cleverness, I think Alphagene is on the right track. Added to his numbers are the fact that obviously, not all sperm live for a week and the ones that do don’t necessarily find the egg. Also, I remember reading that some 25+% of pregnancies end in miscarriage in the first week or so due to hormonal changes and the like without the woman ever knowing she was pregnant. I’d have to find a cite on that, so if you don’t want to believe it, feel free.
All in all, it’s like crziness during the full moon – you only hear about the girl who got knocked up the first time and never about the girl who’s been doing it since 14 without a child to show for it.
“I guess one person can make a difference, although most of the time they probably shouldn’t.”
Kids who can’t support a child shouldn’t be having sex.
How to Turn a General Question into a Great Debate 101:
handy: your statement is too limited, perchance? Did you really mean to limit it to “kids?”
Also, your simple statement leaves the potential grandparents out of the equation; if the kids’ parents can support more children, should their desires (to or not to) play a part? And if they don’t exercise “parental control,” who should be fiscally responsible?
Getting back to the OP, I would say that there are WAY too many variables involved to get a definitive percentage. There is health of male and female, females ovulation schedule, temp, position, ect. The percentage could change with every couple in every situation. It seems that God does in fact work in mysterious ways.
“Solos Dios basta” . . . but a little pizza won’t hurt.
Oye. The request in the OP was for a real answer. Not a GD. My wife and I tried to concieve for 4 1/2 years. Both Infertility Specialists we worked with quoted the same numbers.
On average, in any given month, two normal healthy adults have a 12 % chance of concieving.
Cartoooniverse.
p.s. we have two amazing kids, both adopted. 
If you want to kiss the sky, you’d better learn how to kneel.
My 2¢:
I think this is unanswerable.
The only way to know this for sure is to have closely monitored groups.
Don’t know if that’s ever been done.
And remember, statistics apply only to populations.
In an individual case, it’s either 0% or 100%.
Not a lot of fudge room.
If you think about it, aren’t any odds really just 50/50? Either you will, or you won’t.
If you play with fire…
Linney sez:
What? That’s mind-numbingly incorrect.
[ul]
[li]Either I will get killed in a car accident today, or I won’t. 50/50.[/li][li]Either I will get hit by an asteroid while walking out of the convenience store with my winning lottery ticket while a flock of pigs flies by, or I won’t. 50/50.[/li][/ul]
Mjollnir sez:
I don’t know for sure about the group experiments.
As for statistics only applying to groups, that is only true in some senses. After an event has occurred, your 0% or 100% statement is correct. However, before your event has occurred, the statistics of a group of similar people give you an idea of your chances. Examples:
[ul]
[li]50% of people with your rare skin condition develop cancer, but only 10% do if they regularly eat carrots. If you eat carrots, you are reducing your risk. Sure you won’t know until after the fact whether you win or not, but you have a better shot at it.[/li][li]Everyone who has ever tried to climb Mt. Fujiyumyum has died. All 32000 of them, all of whom were better equipped and more experienced than you. What do you think your chances are of making it to the top?[/li][/ul]
You are absolutely correct about the chances of an event that has already occurred - but the probability of a future event can still be weighed using statistics.
I would imagine that anyone who ever developed a birth-control pill would have been required by the gummint to do various tests to determine whether or not the pill works, and those tests would have required a control group, no? So let’s find out what the stats are for the control group!
One way to do it might be to poll a group of healthy women or couples who are sexually active and have or have not gotten pregnant. Add up the total number of months of sex, add up the total number of pregnancies, and devide pregnancies by months.
Of course, the couples would have to also meet your criterion of having sex only one random time per month, and most couples I know anything at all about do it more than that. I don’t know of any studies with this particular criterion, but if anyone here fits it, post yer stats and I’ll be glad to calculate for the group.
As for me, my motto is “baby-free, way to be”.
The contraceptive sites I’ve checked say the failure rate for the rythm method can reach 24%, in other words a woman has a 24% chance to get pregnant within a year. That’s about 2% per month. There are so many variables that I’m not sure how useful that statistic is, but it seems to be widely quoted. I couldn’t find any statistics that correlated copulation rate with birth rate.
don’t rely on rhythem method unless you are trying to get pregnant, your married, or have a stable longterm relationship in which you would like to have children.
I have one friend who is now 2months along, in a stable long term relationship, they were engaged before she conceived, but the baby wasn’t planned.
And another who probably isn’t, unsafe sex about a week after last period ended, but could be.
My ex got the girl he cheated on me with pregnant, one night he wasn’t as careful as he was with me–I guess she was stupid too, not taking the MorningAfter Pill.
Don’t be stupid people, condoms and the pill, and foam, and abstinance are great methods for not getting pregnant
Don’t take unnecessary risks if you can’t deal with the consequences.
I am a fire whose flames lick and spit at the boundless sky forever desiring wonderous consummation
-me